Beam Transmission Efficiency Research Articles

Investigation on the transmission attenuation of Bessel-Gaussian beams in a dusty environment

This paper delves into the transmission dynamics of Bessel-Gaussian (BG) beams in three distinct dusty environments, leveraging the Generalized Lorenz-Mie Theory (GLMT) alongside a single scattering model for a comprehensive analysis. Through numerical simulations, the study explores the interaction between dust particle scattering and the attenuation and transmittance behaviors of BG beams, elucidating the influences of varying particle concentrations and visibility conditions typical of floating dust, blowing sand, and sandstorms. The findings reveal numerous determinants, including particle number concentration, optical visibility, wavelength, orbital angular momentum (OAM) modes, waist radius, cone angle, and polarization states, which significantly affect the transmission performance of BG beams in dusty conditions. Notably, the attenuation rate decreases with increasing wavelengths and higher OAM modes, thereby extending effective transmission distances. Furthermore, the strategic use of linear polarization emerges as an optimal approach for enhancing BG beam transmission efficiency in dust-rich environments. These insights are crucial for optimizing BG beam transmission in real-world applications, marking a significant advancement in the field.

Propagation properties of the partially coherent radially polarized twisted beam through optical system in turbulence atmosphere

In this paper, the transmission properties of the partially coherent radially polarized twisted (PCRPT) beam propagating in the turbulence atmosphere are investigated. The analytical formulas for the components of the cross-spectral density matrix for the PCRPT beam passing through the optical system in the turbulent atmosphere are developed using the Collins integral and aperture function. Research results indicate that modifying the variable parameters and dimensions of the optical system can control the near-field and far-field distributions of the beam, while providing a more flexible choice of receivers for the PCRPT beam in the receiving plane. By utilizing the Cassegrain reflector system and adjusting the optical system parameters, it is possible to achieve collimated transmission of the PCRPT beam and significantly enhance the beam transmission efficiency in turbulent atmospheric conditions. The derivation process and the research results presented in this paper can be expanded to analyze the application of optical systems to control high-dimensional beam field variations. The envisioned utilization of the results obtained from this research investigation pertains to the fields of beam shaping and optical communications.

A simple method for pulse contrast enhancement via self-focusing

Abstract Here we report on a simple-to-implement and cost-effective approach for laser pulse contrast enhancement, based on the ${\chi}^{(3)}$ nonlinear self-focusing effect. An intentionally induced and gently controlled self-focusing in a thin glass transforms the time-dependent intensity into variation in beam divergence. Followed by a spatial discriminating filter, only the strongly focused fraction traverses the setup, at the expense of efficiency. A numerical model, accounting for the pulse and material parameters via a Gaussian ABCD matrix, provides an estimate for the instantaneous beam waist and transmission efficiency, which enables us to evaluate the resulting contrast enhancement. The estimated contrast enhancement spans between 0.5 and 2.5 orders of magnitude, in conjunction with approximately 25%–90% estimated efficiency, depending on the pulse parameters. In a preliminary experiment we demonstrated the effect with 10s-μJ sub GW regime with approximately 40 $\%$ efficiency and a contrast improvement of more than or equal to 20 dB.

Beam dynamics and cavity design of an 8 MeV CW IH-DTL for SYSU-PAFA

As a part of the Particle Accelerator Facility at Sun Yat-sen University (SYSU-PAFA), a 200 MHz drift tube linac (DTL), operating under continuous wave (CW) mode, has been designed. PAFA-DTL is expected to accelerate a 10 mA proton beam from 2.5 MeV to 8 MeV. Using the alternative phase focusing (APF) beam dynamics scheme, a compact cell array has been designed and optimized in order to limit the cavity length to 2.4 m with high acceleration efficiency. As a result, PAFA-DTL contains 31 acceleration cells with beam transmission efficiency reaches 100%, and better output beam quality is obtained by optimizing the input beam parameters. Interdigital H-mode (IH) structure is utilized in the PAFA-DTL cavity, which has achieved a high unloaded quality factor of 13987. Additionally, to ensure the stability of PAFA-DTL under CW operation, a low Kilpatrick factor (Kp) of 1.42 is obtained by adjusting the blending radius of the drift tubes (DTs) to reduce the risk of RF breakdown. The gap voltage distribution through RF design is compared with that from the beam dynamics, and the maximum absolute value of deviation is only 0.73%. In this paper, the detailed design and results of PAFA-DTL, including beam dynamics and RF design, are presented.

Passage of a focused electron beam generated by a forevacuum plasma source through a narrow extended metal cavity

We report on our investigations of the distribution of diameter of a focused electron beam along the propagation direction at the forevacuum pressures as a function of beam parameters and working gas pressure. The influence of electron beam parameters on the fraction of current transported through a narrow, extended tube is considered. We find that the angles of convergence and divergence of the focused beam depend on the position of the beam crossover point, and that maximum beam transmission through the tube is ensured at lower gas pressure and higher beam accelerating voltage. Up to 90% beam transmission efficiency is obtained for beam transport through a metal tube with diameter 8 mm and length 30 cm.

First injector commissioning results with helium beam at MedAustron Ion Therapy Center

MedAustron is a synchrotron-based Particle Therapy Accelerator located in lower Austria which delivers clinical proton and carbon beams in the range of 62-252.7 MeV/u and 120-400 MeV/u respectively in two clinical treatment rooms. A proton Gantry was recently commissioned in a third clinical treatment room and a fourth experimental beamline is dedicated to non-clinical research activities. Within the latter, the injector commissioning has recently started for He2+ beam generation. The long-term goal is to use helium for cancer treatment due to its favourable physical and biological properties. The helium beam properties from the source up to injection further downstream into the accelerator, i.e. from the Low Energy Beam Transfer line to the Linear Accelerator are discussed in terms of beam emittance, intensity and transmission efficiency. Furthermore, a comparison with simulated data is presented.

A beam dynamics study for efficient extraction from the VECC K500 superconducting cyclotron

Beam extraction from the K500 superconducting cyclotron is very challenging due to its long extraction path of about 330° with very high magnetic field gradient and low acceptance. The initial attempts of beam extraction showed that the pilot beams could successfully clear only a few magnetic channels. To investigate the causes of the beam loss, magnetic field measurements in different zones of the cyclotron were repeated. The total field has been generated by superposition of the measured field and the numerically computed field of the extraction elements. Based on these data, extensive beam dynamics simulation has been carried and beam distribution at the entry of the extraction path obtained by accelerated orbit calculations. The energy spread due to multi-turn deflector entry has been included in the simulation. The beam envelope along the extraction path as well as the beam transmission efficiency has been determined for different positions of the extraction elements. The radial positions of the extraction elements have been optimized parametrically to compute the maximum transmission efficiency. The present studies have enabled us to successfully extract the pilot beam (N4+) from the cyclotron with beam current of around 20 enA.

Study of Beam Transmission Efficiency in Injection and Ramping Process of the HEPS Booster

Study of Beam Transmission Efficiency in Injection and Ramping Process of the HEPS Booster

Design, fabrication and relative bunch length measurement of S-band pre-buncher

A 10 MeV, 3 kW RF electron linear accelerator (linac) is in operation at EBC, Kharghar. A new horizontal linac rated for 10 MeV, 5 kW has been planned to be developed at EBC, Kharghar. The components of 10 MeV linac beam line consists of electron gun, a standing wave (SW) single cell pre-buncher cavity and a SW main linac cavity of length 0.9 m. In order to enhance the beam capture efficiency and to reduce the energy spread a pre-buncher cavity along with focusing elements will be introduced between the electron gun and the main linac cavity section. In this work the design simulation, fabrication, RF measurements and beam experimental trials of the 2856 MHz low Q, wide band pre-buncher cavity is presented. The measured RF parameters of pre-buncher cavity are f0=2854.4 MHz in air, QL=600, tuning range ±2.5 MHz. Electron beam transmission efficiency of 99% is achieved with minimum relative bunch length obtained at 400W of input RF power.

Optimization of a B[formula omitted]C/graphite composite energy degrader and its shielding for a proton therapy facility

Proton therapy is an advanced cancer treatment modality due to its ability to precisely deliver radiation doses to tumors using the Bragg peak effect. An energy degrader plays a vital role at a cyclotron-based proton therapy facility, as it provides a rapid, reliable, and reproducible method of setting the appropriate beam energy for radiotherapy. However, the protons undergo nuclear interactions with the matter in the degrader, leading to significant secondary particles causing a large ambient radiation dose nearby, creating severe risks for the facility operation. This study investigated the beam loss mechanism and the secondary particle generation in a B4C/graphite composite (BGC) energy degrader. Monte Carlo simulations were performed to ensure the shielding design’s reliability. Calculations showed that the BGC degrader had a higher beam transmission efficiency than a pure graphite degrader, while the secondary neutron yield was higher. An optimum shielding configuration can significantly reduce the radiation dose to an acceptable level for sensitive devices and maintenance staff.

An Axial Foilless Diode Guided by Composite Magnetic Field for the Production of Relativistic Electron Beams

Foilless diode are widely used in high-power microwave devices, but the traditional foilless diodes have large volume, heavy weight, and high power consumption, which are not conducive to the application of high-power microwave system on mobile platform. In order to reduce the size of the foilless diode, improve the transmission efficiency of electron beams, and reduce the weight and power consumption of the guiding magnetic field system, an axial foilless diode with a composite guiding magnetic field system is developed in this paper. By adjusting the structure size and magnetic field parameters of solenoid coil, permanent magnet, and soft magnet, the configuration of the composite magnetic field is optimized. The diameter of the anode tube is about 40% smaller than that of the original structure, and the weight and power consumption of the guiding magnetic system are about 40% lower than that of the original system when the same axial magnetic field intensity in the uniform region is generated. When the magnetic field strength of the permanent magnet is set as 1.4 T and that of the solenoid coil is in the range of 0.5 T∼1 T, the electron beam transmission efficiency is 100%, and the diode impedance is adjustable in the range of 100 Ω∼240 Ω. The experimental results verify the correctness of the simulation analysis. The experimental results show that when the magnetic field strength of the solenoid coil is 0.98 T (0.5 T) and that of the permanent magnet is 1.4 T, the transmission efficiency of the high-current annular electron beam with a peak voltage of 636 kV (590 kV) and a peak current of 3.3 kA (2.6 kA) is 100%, and the diode impedance is about 194 Ω (220 Ω).

Study of the conditions for the effective initiation of plasma-chemical treatment of flue gas under the influence of a pulsed electron beam

AbstractThis paper presents the results of comprehensive studies of the efficiency of a pulsed electron beam transmission through a mixture of gases: nitrogen (83%), carbon dioxide (14%), and oxygen (2.6%) in the presence of ash and water vapor. The studied concentrations correspond to the concentrations of nitrogen, oxygen, and carbon dioxide in flue gas. The pressure and concentration of water vapor and ash in the drift chamber varied (375, 560, and 750 Torr; humidity 15 ± 5% and 50 ± 15%). The charge dissipation of a pulsed electron beam in the gas mixture in the presence of ash and water vapor was investigated, as well as the effect of the concentration of water vapor and ash on the geometric profile of the pulsed electron beam.

Polarized beam option for the time-of-flight spectrometer NEAT

We present the basic design of the incoming neutron beam polarizer system recently installed at the TOF spectrometer NEAT at HZB and the first experimental test results. The recent upgrade of the instrument resulted in beam flux on the sample, which is one of the highest worldwide for this class of instruments. The substantial intensity gain obtained in the upgrade provides good conditions for polarized neutron experiments, considering the inherent cuts of neutron intensity by polarizing the beam. The neutron beam polarizer is placed inside a 3.8 m long evacuated neutron “guide changer”, which allows us to move into the beam delivery guide one of 3 alternative straight neutron guide sections mounted in parallel on a linear translation stage. The new transmission polarizer takes up the inside volume of a 1.33 m long, 60 mm x 125 mm cross section straight guide portion. The focusing of the beam after the polarizer to the 30 mm x 50 mm sample area happens over a total length of 3.5 m, of which 2.92 cm is a converging guide assembly with m=4 supermirror coating and parabolic end. This guide section leaves 58 cm space between guide exit and sample axis for sample environment equipment, in particular for high field cryomagnets. The transmission polarizer contains 8 “V cavity” channels with non-polarizing supermirror coated, opaque side walls and neutron-transparent Si cavity plates, coated by m=3 polarizing supermirror on both sides. The nominal operational wavelength band width of the polarizer is 2.5 – 8 Å, with measured polarization efficiency between 92 and 96 % for well collimated beam. The beam transmission efficiency for the preferred neutron spin state is about 65 %. The first 110 cm of the neutron spin guide field after the exit of the polarizer is provided by the stray fields of the magnet around the polarizer and of a permanent guide field magnet acting in the same direction. This section contains a wavelength tunable single coil Mezei flipper with flipping efficiency > 99 %. The rest of the guide field magnets are solenoids around the glass neutron beam guide. The supermirror coating in the polarized neutron section of the beam guide has been manufactured using a non-magnetic Ni alloy, the guide exchanger housing and its mechanical parts are made of non-magnetic alloys, primarily stainless steel. The polarized beam delivery system is by now operational and it is available for polarized neutron beam experiments on samples in a magnetic field. A 14 T vertical field cryomagnet is on hand at the HZB Sample Environment Group for use on NEAT. The NEAT sample chamber has been designed and built with non-magnetic or weakly magnetic materials in order to allow both for polarized neutron beam experiments and for polarization analysis work.

Study of an energy degrader made of B4C/graphite composites.

The HUST-PTF (proton therapy facility in Huazhong University of Science and Technology) is now under construction based on an isochronous superconducting cyclotron at Huazhong University of Science and Technology. Because the energy extracted by the cyclotron is fixed, an energy degrader is necessary to modulate the beam energy after the cyclotron for clinical requirements. However, the multiple Coulomb scattering that occurs in the degrader increases the beam emittance. Therefore, collimators are designed after the degrader to decrease the beam emittance. Because of the severe beam losses in the aforementioned energy degradation and emittance restriction, the main design consideration is improving the beam transmission efficiency. In this note, a novel energy degrader made of B4C/graphite composite (BGC) is studied regarding its material fabrication, improved beam transmission efficiency, energy degradation, emittance growth, and secondary-neutron yield using the Geant4 Monte Carlo software. Moreover, the thermal properties of the BGC degrader are analyzed. Finally, for a degrader with 40% boron content, the emittance after the degrader decreases by 5.5% and the transmission efficiency after the final collimator increases by 15.9% at 70 MeV compared with a pure-graphite degrader.

Stacked dual beam electron optical system for THz integrated wideband traveling wave tube

In this paper, a stacked dual beam electron gun and the associated electron optical system are proposed. The stacked dual beam electron gun includes two compact focusing electrodes which help to achieve dual sheet beams. As an application of this dual beam electron gun, a 340 GHz integrated dual beam traveling wave tube (TWT) based on the staggered dual vane slow-wave structure (SWS) is also put forward. In order to reduce the length of the TWT, a novel input/output coupler is introduced. The overall transmission characteristics of the SWS structure together with the input/output couplers show a wide bandwidth covering a frequency range of 306 GHz to 360 GHz. Based on the parameters obtained for the integrated TWT, a stacked dual-beam electron gun with dual focusing electrodes is designed to achieve a beam current of 43 mA, a beam voltage of 21.4 kV, and a cross-sectional size of each beam of 0.3 mm × 0.08 mm. A uniform magnetic field of 0.52 T is utilized to focus the dual electron beams, and a beam transmission efficiency of 97.1% is achieved over a length of 50 mm. Finally, particle in cell simulation results show that the integrated dual-beam TWT can generate an output power of 5 W over the frequency range of 315 GHz to 350 GHz, with the maximum output power of 24.5 W at 330 GHz.

Development of 2.45 GHz ECR ion sources at IMP

The Ion Source Group at IMP has been undertaking a series of high intensity ion beam R&D projects. The first project is the development of the intense proton source and its low energy beam transport system (LEBT) for China Initiative Accelerator Driven Sub-Critical reactor (CiADS). The specific characteristics of the proton source are long-term reliability and flexible beam manipulation for the commissioning need of the Superconducting radio-frequency (SRF) accelerators. The LEBT is used to deliver 35 keV H+ beam to the entrance of a 2.1 MeV RFQ . And then the 2.1 MeV proton beam is further accelerated by the superconducting cavities to 25 MeV and eventually goes into a high power beam dumper. Another project is the development of the intense ion source for Jinping Underground Nuclear Astrophysics experiments (JUNA). The ion source was expected to provide 10 emA H+, 10 emA He+ or 2.5 emA He2+ beams for the study of (p, γ), (p, α), (α, p) and (α, γ) reactions in the first phase of the JUNA project. The main challenges of the ion source for JUNA project are production of intense He2+ beam, control of the beam contaminations and beam commissioning a wide beam energy range (70∼800 keV) . In this paper, the studies of these intense beam injector systems, for instance, beam intensities, species and ratio, beam transmission efficiency in the LEBT and also the beam optics matching to the downstream accelerator systems will be presented.

Optimal Resonant Beam Charging for Electronic Vehicles in Internet of Intelligent Vehicles

To enable electric vehicles (EVs) to access to the Internet of Intelligent Vehicles (IoIV), charging EVs wirelessly anytime and anywhere becomes an urgent need. The resonant beam charging (RBC) technology can provide high-power and long-range wireless energy for EVs. However, the RBC system is unefficient. To improve the RBC power transmission efficiency, the adaptive RBC (ARBC) technology was introduced. In this paper, after analyzing the modular model of the ARBC system, we obtain the closed-form formula of the end-to-end power transmission efficiency. Then, we prove that the optimal power transmission efficiency uniquely exists. Moreover, we analyze the relationships among the optimal power transmission efficiency, the source power, the output power, and the beam transmission efficiency, which provide the guidelines for the optimal ARBC system design and implementation. Hence, perpetual energy can be supplied to EVs in IoIV virtually.

Study on Improvement of Injected Power for EAST-NBI

In order to meet experimental requirements on high parameter plasma research, the injected power of the counter injector is expected to increase at a fixed beam energy of 50 keV for deuterium neutral beam. Three candidate schemes are compared to assess the possibilities of raising the injected power. Considering safety and economic factors, raising the electric field in the first gap is employed by adjusting the voltage gradient on the accelerator. The experiments show that the optimum perveance is increased from 2.2 to 2.7 μP by changing of gradient grid voltage from 0.84 to 0.78 Vacc. The ion beam power is promoted by about 50% at 3.0 μP, but beam transmission efficiency decreased to 60% at 3.0 μP. Thus, the injected power is boosted about 25%.

Commissioning of the FRIB RFQ

The radio-frequency quadrupole (RFQ) at the Facility for Rare Isotope Beams (FRIB) is a 4-vane type cavity designed to accelerate heavy ion beams with charge states Q/A between 1/7 and 1/3 from 12 keV/u to 0.5 MeV/u. The RFQ was assembled in the FRIB tunnel in November 2016. Bead-pull measurements and tuning were performed with low RF power. The RFQ has been conditioned to 59 kW in August 2017, which is sufficient to accelerate the Key Performance Parameter (KPP) beams, Argon and Krypton. The RFQ has been successfully commissioned with KPP beams in CW regime in October 2017. 40Ar9+ and 86Kr17+ beams were accelerated by the FRIB RFQ in the CW regime to the designed energy of 0.5 MeV/u. With the multi-harmonic buncher operational, the FRIB RFQ commissioning has been completed with bunched beam in February 2018. The beam transmission efficiency through the RFQ was in good agreement with PARMTEQ simulation results. The detailed results from the FRIB RFQ tuning, high power conditioning and beam commissioning will be presented in this paper.

Layout and performance of the FCC-ee pre-injector chain

The Future Circular e+e− Collider pre-injector chain consists of a 6 GeV S-Band linac, a damping ring at 1.54 GeV and pre-booster ring to reach 20 GeV for injection to the main booster. The electron and positron beams use the same accelerator chain alternatively. The e−beam is generated from a novel low level RF-gun providing 6.5 nC charge at 11 MeV with 0.5 micron geometric emittance. The e+ beam is produced by the impact of a 4.46 GeV e− beam onto a hybrid target, accelerated in the linac up to 1.54 GeV, and injected to the damping ring for emittance cooling. Simulations on the performance of the DR are presented for reaching the required equilibrium emittances at the required damping time. As an alternative option, a 20 GeV linac is considered utilising C-Band cavities and simulations studies have been undertaken regarding the beam transport and transmission efficiency up to that energy.